Aquaculture

Question 1

What is aquaculture? What is fish farming?

Answer 1

Cultivation of aquatic organisms such as fish, shellfish and algae using intensive or extensive methods in order to increase production yield to above that normally found in the environment
Fish farming is aquaculture restricted to fish

Question 2

What are the types of aquaculture?

Answer 2

Extensive farming - large areas are farmed with low stocking densities and much reliance on natural productivity e.g. Carb and oysters
Intensive farming - fish held in high densities in small units with a total dependence on supplied feed e.g. trout and salmon
Sea ranching - Juvenile fish are reared extensively or intensiveley for release into natural waters to fend for themselves e.g. salmon

Question 3

What are the three types of intensive farming systems?

Answer 3

Land based tanks - water renewal from rivers or tides
- recirculating systems (environmentally sound but expensive to operate)
Floating cages - fixed sublittoral enclosures (bags hung from pontoon)
Midwater pens - cages moored beneath the surface

Question 4

Why are the highlands and islands of Scotland naturally rich in fish?

Answer 4

Effects of the gulf stream
Clean unpolluted water
Refuge to wildlife and sensitive to human intrusion
Lack of mineral resources, hostile climate, long distance from markets all make economic development in these areas risky

Question 5

Describe the rapid growth of salmon farming

Answer 5

mid 1960s - Atlantic salmon farming pioneered in Norway
mid 1970s - commercial production of domesticated Scottish stock achieved by marine harvest at L. Ailort, Invernesshire
1979 - 500t of salmon produced from 14 seawater sites
1990 - 30,000t from 360 farms owned by 170 companies
2004 - 330 sites producing > 140,000t

Question 6

What are the monetary value of salmon and shellfish?

Answer 6

Global market of farmed Scottish salmon is worth £382 million
Shellfish contributes £160 million to the economy

Question 7

What criteria make for a good commercially cultured fish?

Answer 7

Ability to reproduce in captivity
Simple larval development
Relatively fast growth rate
Food requirements that are readily satisfied
Efficient and economic food conversion
Hardiness and resistance to stress of confinement
Lack of aggression or territorial behaviour

Question 8

What local factors are important in the set-up of a aquaculture farm?

Answer 8

Availability of suitable sites
Reliable supply of unpolluted water
Appropriate temperature for growth
Availability of fry (wild or other) for stocking
Freedom from pests
Demand for product

Question 9

What are the top 6 species in world aquaculture? and tonnage as of 2004

Answer 9

1 - Carps and other cyprinids (18mt) 
2 - Oysters (4.6mt)
3 - Clams, cockles and arkshells (4.1mt)
4 - Misc. freshwater fishes (3.7mt)
5 - Shrimps and prawns (2.5mt)
6 - Salmons, trouts and smelts (2mt)

Question 10

What are the characteristics of the Family Salmonidae?

Answer 10

Trout and Salmon
Relatively primitive species
Originated in FW and all return to FW to breed
Native to higher latitudes of N.Hemisphere
2 groups of salmon, Atlantic and Pacific

Question 11

Name 4 types of salmonids

Answer 11

Atlantic salmon (Salmo salar)
Brown Trout (S.trutta)
Pacific salmon (6spp) (Oncorhynchus spp.)
Rainbow Trout (O.mykiss)

Question 12

Name the various stages of a salmons life cycle

Answer 12

Eggs
Eyed eggs
Alevin
Fry
Parr
Smolt
Adult

Question 13

What is the farmed life cycle of salmonids?

Answer 13

Broodstock fish transferred to FW and stripped of eggs and milt (November)
Fertilised eggs kept in baskets, trays, jars etc, in flowing well oxygenated water at 1-12 Degrees C
Midterm incubation embryonic eye becomes visible and eggs can be moved
Alevins or Fry moved to tanks/raceways in Jan/Feb
Fed artificial diet
Net cages in FW until ready to adapto to SW (smolts)
Smolts moved to marine cages at 30-50g
Grow rapidly in SW
Most fish take another year, males 2-3kg females 5kg

Question 14

What is the difference between a freshwater fish and a saltwater fish?

Answer 14

FW - passively lose ions TO environment and gain water
- Main organs involved in regulation gills, intestine and kidney
- dilute urine and “active” ion uptake at gills
SW - Passively gain ions and lose water to environment
- main organs in regulation gill, intestine and kidney
- Drink seawater and secrete ions at gills

Question 15

What are the stats regarding other farmed fish?

Answer 15

Brown Trout - 175t (2002) for re-stocking
Raibow trout - 7,500t (2006) 88% for food, 12% re-stocking
Cod (Gadus morhua) - 2,900t (2007)
Halibut (Hippoglossus hippoglossus) - 233t (2006)

Question 16

What are the main points about cod farming?

Answer 16

Cod eggs have no yolk to sustain them in earliest stages and require tiny live feed from the start
Juvenile cot tend towards cannibalism
2 cod hatcheries in Scotland - Mull of Kintyre and Sheltand
2008 - Worlds first organic cod farm goes into administration with 40m debt

Question 17

What are the challenges of halibut farming?

Answer 17

Juvenile production - complicated larval rearing
- quality of juveniles
- disease
On Growing 
- Needs surface area for growth
- long growth cycle
- capital intensive production

Question 18

Why is halibut metamorphosis a problem?

Answer 18

Halibut larvae go through a complex change from symmetric larvae (round fish) to an asymmetric juvenile (flatfish)
Deficient nutrition before and during metamorphosis results in poorly developed fish
- Poor eye migration
- Malpigmented fish